We propose to develop a clinic- and home-based behavioral intervention to promote weight management and improve physical activity, diet and sedentary behaviors among preadolescent and adolescent youth who are survivors of childhood ALL (defined as being off therapy for at least 2 years without relapse). Children who survive acute lymphoblastic leukemia (ALL) have an increased risk for development of overweight and obesity with the prevalence in this population reported as high as 57%. Identified mechanisms that may contribute to the risk of obesity in the childhood ALL population include factors related to their underlying ALL and its treatment as well as modifiable factors such as excess energy intake, reduced energy expenditure, and sedentary lifestyle. Because of the unique health and psychosocial challenges faced by these children interventions to prevent and treat their obesity need to be developed and tested. The experimental intervention we propose to evaluate will be tailored specifically for pediatric survivors of ALL, be grounded in formative work with this group and their caregivers, and build upon prior successful research on weight reduction and related behaviors by the research team. We hypothesize that because the intervention will the tailored to the unique needs of childhood survivors of ALL, it will promote greater change in BMI z-score, a metric of relative weight status, as compared to an intervention developed for otherwise healthy children. Testing of the intervention will be performed via a small, randomized, controlled trial (RCT) among at risk for overweight and overweight (>85% BMI for age and sex) preadolescent and adolescent youth (10-16 years) with a prior history of childhood acute lymphoblastic leukemia. The RCT will compare the experimental intervention to an intervention that has been proven efficacious in increasing healthy behaviors and reducing excess weight among healthy overweight and obese adolescents. Our primary aim is to determine, at 4 months, the impact of this intervention on BMI z-score as compared to an Enhanced Standard Intervention (ESI). Secondary aims are to determine the impact of the intervention vs. ESI on self-reported behavioral measures of diet and physical activity, selected metabolic and physiologic measures, quality of life and depression measurements, and use and acceptability of the intervention by participants, their families and participating clinical staff. Children who survive ALL have an increased risk for development of overweight and obesity that in part is due to the treatment for their ALL. No proven interventions exist to prevent or treat overweight in this unique population and research on the importance of tailoring behavioral interventions to the characteristics of the underlying population suggest that weight control programs successful among healthy children might not work for this group. This research aims to develop and pilot test a specific weight control intervention for pediatric survivors of ALL.